In 2003, fearing that overworked medical residents were committing errors due to fatigue, the Accreditation Council for Graduate Medical Education put limits on how many consecutive hours residents could work on a shift.

Now, ten years later, it's not clear the change has had the desired effect.

One study, led by Sanjay Desai at Johns Hopkins, randomly assigned first-year residents to either a 2003- or 2011-compliant schedule. While those in the 2011 group slept more, they experienced a marked increase in handoffs, and were less satisfied with their education. Equally worrisome, both trainees and nurses perceived a decrease in the quality of care—to such an extent that one of the 2011-compliant schedules was terminated early because of concerns that patient safety was compromised. And another study, comparing first-year residents before and after the 2011 changes, found a statistically significant increase in self-reported medical error.

While these studies suggest the complex nature of patient safety—that manipulating one variable, like hours worked, inevitably affects another, like the number of handoffs—there is another tradeoff, more philosophical than quantifiable. It has less to do with the variables within the system and how we tinker with them, and more to do with what we overlook as we focus relentlessly on what we can count.

Caveat: this essay by Lisa Rosenbaum in the New Yorker is a bit short on data for my liking, the above study feeling like just one insufficient data point.

But the meta point about unintended consequences and complexity is worth noting. The increase in handoffs of patients, the decrease in time any one doctor spends with a patient, these all have consequences that work against the quality of healthcare, even as I believe more well-rested residents are a good thing, many of my doctor friends having been put through grueling rotations.